If you ever used an older version of Mac OS X (Tiger, Leopard or Snow Leopard), you would notice that there was a Library folder in your Users folder. As most power uses would know, this folder holds important information like Application Settings, game save files and so on. If you upgraded to Lion, you'd notice the folder is hidden by default. Here's how to make it visible again.

1. Launch Terminal (Applications -> Utilities)
2. Make the folder visible by doing this command and hitting enter:
chflags nohidden ~/Library/
You can close Terminal now and you'll notice the Library folder is visible again! If you want to hide so novice users don't make a mess of it, just do this command in Terminal:
chflags hidden ~/Library/